Cloud altitude measuring apparatus

Abstract

Cloud altitude measurement is carried out in a step-by-step manner wherein the measuring distance is changed by a predetermined amount for each measurement step. First and second integrators respectively integrate reflected echo signals during respective first and second time intervals T 1 , T 2 with T 1 <T 2 . The first integrator integrates reflected light pulses and noise and the second integrator integrates noise. The difference between the integrated signal outputs from the first and second integrators is determined by a summation device and a controllable level-sensing signal evaluating device emits a signal if the aforesaid difference exceeds a predetermined value. The signal evaluating device is controlled to emit the indicating signal when a number of consecutive measurement steps have been measured. The first and second integrators can be controlled to integrate over a plurality of consecutive measurement steps before being reset to zero or alternatively, integration is performed over one or more measurement steps at a time. In the latter case, the measuring apparatus further comprises an analog/digital convertor connected to the output of the summation device, an accumulator, and the digital output signal from the analog/digital convertor is transferred to the accumulator and the evaluation device after the predetermined number of measurements. The measurement apparatus can be further modified to include a shift register connected to the output of the analog/digital convertor and an accumulator having inputs respectively connected to the input and output of the shift register and wherein a timing circuit actuates the level-sensing signal evaluating device to examine the contents of the accumulator after each measurement step.

What is claimed is: 
     
       1. Cloud altitude measuring means, in which the measurement is carried out step-by-step and the measuring distance is changed by a predetermined value for each measurement step, comprising a signal emitter for emitting a series of light pulses for each measurement step; a signal receiver for receiving echo signals generated by the emitted light pulses upon reflection against an object, the reflected light pulses including noise; first and second integrators for integration of echo signals and noise received in respective first and second time intervals, said first and second integrators integrating reflected light pulses; a summation device for determining the difference between the integrated signal outputs from said first and second integrators; a controllable level-sensing signal evaluating device for emitting a signal if the difference between said integrated signal outputs exceeds a predetermined value; means for controlling said signal evaluating device to emit an indicating signal when a number of consecutive measurement steps have been measured; and said controlling means resetting said first and second integrators to zero. 
     
     
       2. Means according to claim 1, wherein said means for controlling also controls said first and second integrators to integrate echo signals and noise from a plurality of consecutive measurement steps before being reset to zero. 
     
     
       3. Means according to claim 1, wherein said means for controlling controls said first and second integrators to integrate echo signals and noise from at least one of said measurement steps at a time, and resetting said first and second integrators between each measurement of at least one measurement step, and further comprising an analog/digital convertor connected to the output of said summation device; an accumulator; said means for controlling transferring the digital output signal from said analog/digital convertor to said accumulator and said means for evaluating after a predetermined number of measurements; and said means for evaluating emitting a signal if the contents of said accumulator exceed a predetermined value. 
     
     
       4. Cloud altitude measuring means according to claim 1, wherein said means for controlling controls said first and second integrators to integrate echo signals and noise from one measurement step at a time, and resetting said first and second integrators after each said measurement step; and further comprising a shift register and an analog/digital convertor, said analog/digital convertor being connected to the output of said summation device, and said shift register being connected to the output of said analog/digital convertor; an accumulator having one input thereof connected to the input of said shift register and another input connected to the output of said shift register, said means for controlling including a timing circuit for actuating said level-sensing signal evaluating device to evaluate the contents of said accumulator after each measurement step and to emit a signal if said contents exceed a predetermined value.